11.2 Discussion

When installing MS Windows NT4/200x on a computer, the installation program creates default users and groups, notably the Administrators group, and gives that group privileges necessary privileges to perform essential system tasks , such as the ability to change the date and time or to kill (or close) any process running on the local machine.

The Administrator user is a member of the Administrators group, and thus inherits Administrators group privileges. If a joe user is created to be a member of the Administrators group, joe has exactly the same rights as the user, Administrator .

When an MS Windows NT4/200x/XP machine is made a Domain Member, the " Domain Admins " group of the PDC is added to the local Administrators group of the workstation. Every member of the Domain Administrators group inherits the rights of the local Administrators group when logging on the workstation.

The following steps describe how to make Samba PDC users members of the Domain Admins group?

1. Create a UNIX group (usually in /etc/group ), let's call it domadm .

2. Add to this group the users that must be " Administrators ". For example, if you want joe , john and mary to be administrators, your entry in /etc/group will look like this:

    domadm:x:502:joe,john,mary 

3. Map this domadm group to the " Domain Admins " group by running the command:

    root# net groupmap add ntgroup=Domain Admins UNIXgroup=domadm 

The quotes around " Domain Admins " are necessary due to the space in the group name . Also make sure to leave no white-space surrounding the equal character (=).

Now joe , john and mary are domain administrators.

It is possible to map any arbitrary UNIX group to any Windows NT4/200x group as well as making any UNIX group a Windows domain group. For example, if you wanted to include a UNIX group (e.g., acct) in an ACL on a local file or printer on a Domain Member machine, you would flag that group as a domain group by running the following on the Samba PDC:

 root# net groupmap add rid=1000 ntgroup="Accounting" UNIXgroup=acct 

Be aware that the RID parameter is a unsigned 32-bit integer that should normally start at 1000. However, this RID must not overlap with any RID assigned to a user. Verification for this is done differently depending on the passdb backend you are using. Future versions of the tools may perform the verification automatically, but for now the burden is on you.

11.2.1 Default Users, Groups and Relative Identifiers

When first installed, Microsoft Windows NT4/200x/XP are preconfigured with certain User, Group, and Alias entities. Each has a well-known Relative Identifier (RID). These must be preserved for continued integrity of operation. Samba must be provisioned with certain essential Domain Groups that require the appropriate RID value. When Samba-3 is configured to use tdbsam the essential Domain Groups are automatically created. It is the LDAP administrators' responsibility to create (provision) the default NT Groups.

Each essential Domain Group must be assigned its respective well-kown RID. The default Users, Groups, Aliases, and RIDs are shown in Table 11.1.

N OTE

When the passdb backend uses LDAP ( ldapsam ) it is the admininstrators' responsibility to create the essential Domain Groups, and to assign each its default RID.

It is permissible to create any Domain Group that may be necessary, just make certain that the essential Domain Groups (well known) have been created and assigned its default RID. Other groups you create may be assigned any arbitrary RID you care to use.

Be sure to map each Domain Group to a UNIX system group. That is the only way to ensure that the group will be available for use as an NT Domain Group.

11.2.2 Example Configuration

You can list the various groups in the mapping database by executing net groupmap list . Here is an example:

 root# net groupmap list 

Table 11.1. Well-Known User Default RIDs

Well-Known Entity	RID	Type	Essential
Domain Administrator	500	User	No
Domain Guest	501	User	No
Domain KRBTGT	502	User	No
Domain Admins	512	Group	Yes
Domain Users	513	Group	Yes
Domain Guests	514	Group	Yes
Domain Computers	515	Group	No
Domain Controllers	516	Group	No
Domain Certificate Admins	517	Group	No
Domain Schema Admins	518	Group	No
Domain Enterprise Admins	519	Group	No
Domain Policy Admins	520	Group	No
Builtin Admins	544	Alias	No
Builtin users	545	Alias	No
Builtin Guests	546	Alias	No
Builtin Power Users	547	Alias	No
Builtin Account Operators	548	Alias	No
Builtin System Operators	549	Alias	No
Builtin Print Operators	550	Alias	No
Builtin Backup Operators	551	Alias	No
Builtin Replicator	552	Alias	No
Builtin RAS Servers	553	Alias	No

 Domain Admins (S-1-5-21-2547222302-1596225915-2414751004-512) -> domadmin Domain Users (S-1-5-21-2547222302-1596225915-2414751004-513) -> domuser Domain Guests (S-1-5-21-2547222302-1596225915-2414751004-514) -> domguest 

For complete details on net groupmap , refer to the net(8) man page.